feat: Add OpenMetrics2 configuration support

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/OpenMetrics2Properties.java

@@ -0,0 +1,142 @@
+package io.prometheus.metrics.config;
+
+import javax.annotation.Nullable;
+
+/** Properties starting with io.prometheus.open_metrics2 */
+public class OpenMetrics2Properties {
+
+  private static final String PREFIX = "io.prometheus.open_metrics2";
+  private static final String CONTENT_NEGOTIATION = "content_negotiation";
+  private static final String DISABLE_SUFFIX_APPENDING = "disable_suffix_appending";
+  private static final String COMPOSITE_VALUES = "composite_values";
+  private static final String EXEMPLAR_COMPLIANCE = "exemplar_compliance";
+  private static final String NATIVE_HISTOGRAMS = "native_histograms";
+
+  @Nullable private final Boolean contentNegotiation;
+  @Nullable private final Boolean disableSuffixAppending;
+  @Nullable private final Boolean compositeValues;
+  @Nullable private final Boolean exemplarCompliance;
+  @Nullable private final Boolean nativeHistograms;
+
+  private OpenMetrics2Properties(
+      @Nullable Boolean contentNegotiation,
+      @Nullable Boolean disableSuffixAppending,
+      @Nullable Boolean compositeValues,
+      @Nullable Boolean exemplarCompliance,
+      @Nullable Boolean nativeHistograms) {
+    this.contentNegotiation = contentNegotiation;
+    this.disableSuffixAppending = disableSuffixAppending;
+    this.compositeValues = compositeValues;
+    this.exemplarCompliance = exemplarCompliance;
+    this.nativeHistograms = nativeHistograms;
+  }
+
+  /** Gate OM2 features behind content negotiation. Default is {@code false}. */
+  public boolean getContentNegotiation() {
+    return contentNegotiation != null && contentNegotiation;
+  }
+
+  /** Suppress {@code _total} and unit suffixes. Default is {@code false}. */
+  public boolean getDisableSuffixAppending() {
+    return disableSuffixAppending != null && disableSuffixAppending;
+  }
+
+  /** Single-line histogram/summary with {@code st@}. Default is {@code false}. */
+  public boolean getCompositeValues() {
+    return compositeValues != null && compositeValues;
+  }
+
+  /** Mandatory timestamps, no 128-char limit for exemplars. Default is {@code false}. */
+  public boolean getExemplarCompliance() {
+    return exemplarCompliance != null && exemplarCompliance;
+  }
+
+  /** Exponential buckets support for native histograms. Default is {@code false}. */
+  public boolean getNativeHistograms() {
+    return nativeHistograms != null && nativeHistograms;
+  }
+
+  /**
+   * Note that this will remove entries from {@code propertySource}. This is because we want to know
+   * if there are unused properties remaining after all properties have been loaded.
+   */
+  static OpenMetrics2Properties load(PropertySource propertySource)
+      throws PrometheusPropertiesException {
+    Boolean contentNegotiation = Util.loadBoolean(PREFIX, CONTENT_NEGOTIATION, propertySource);
+    Boolean disableSuffixAppending =
+        Util.loadBoolean(PREFIX, DISABLE_SUFFIX_APPENDING, propertySource);
+    Boolean compositeValues = Util.loadBoolean(PREFIX, COMPOSITE_VALUES, propertySource);
+    Boolean exemplarCompliance = Util.loadBoolean(PREFIX, EXEMPLAR_COMPLIANCE, propertySource);
+    Boolean nativeHistograms = Util.loadBoolean(PREFIX, NATIVE_HISTOGRAMS, propertySource);
+    return new OpenMetrics2Properties(
+        contentNegotiation,
+        disableSuffixAppending,
+        compositeValues,
+        exemplarCompliance,
+        nativeHistograms);
+  }
+
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  public static class Builder {
+
+    @Nullable private Boolean contentNegotiation;
+    @Nullable private Boolean disableSuffixAppending;
+    @Nullable private Boolean compositeValues;
+    @Nullable private Boolean exemplarCompliance;
+    @Nullable private Boolean nativeHistograms;
+
+    private Builder() {}
+
+    /** See {@link #getContentNegotiation()} */
+    public Builder contentNegotiation(boolean contentNegotiation) {
+      this.contentNegotiation = contentNegotiation;
+      return this;
+    }
+
+    /** See {@link #getDisableSuffixAppending()} */
+    public Builder disableSuffixAppending(boolean disableSuffixAppending) {
+      this.disableSuffixAppending = disableSuffixAppending;
+      return this;
+    }
+
+    /** See {@link #getCompositeValues()} */
+    public Builder compositeValues(boolean compositeValues) {
+      this.compositeValues = compositeValues;
+      return this;
+    }
+
+    /** See {@link #getExemplarCompliance()} */
+    public Builder exemplarCompliance(boolean exemplarCompliance) {
+      this.exemplarCompliance = exemplarCompliance;
+      return this;
+    }
+
+    /** See {@link #getNativeHistograms()} */
+    public Builder nativeHistograms(boolean nativeHistograms) {
+      this.nativeHistograms = nativeHistograms;
+      return this;
+    }
+
+    /** Enable all OpenMetrics 2.0 features */
+    public Builder enableAll() {
+      this.contentNegotiation = true;
+      this.disableSuffixAppending = true;
+      this.compositeValues = true;
+      this.exemplarCompliance = true;
+      this.nativeHistograms = true;
+      return this;
+    }
+
+    public OpenMetrics2Properties build() {
+      return new OpenMetrics2Properties(
+          contentNegotiation,
+          disableSuffixAppending,
+          compositeValues,
+          exemplarCompliance,
+          nativeHistograms);
+    }
+  }
+}

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/PrometheusProperties.java

@@ -2,6 +2,7 @@
 
 import java.util.HashMap;
 import java.util.Map;
+import java.util.function.Consumer;
 import javax.annotation.Nullable;
 
 /**
@@ -21,6 +22,7 @@ public class PrometheusProperties {
   private final ExporterHttpServerProperties exporterHttpServerProperties;
   private final ExporterOpenTelemetryProperties exporterOpenTelemetryProperties;
   private final ExporterPushgatewayProperties exporterPushgatewayProperties;
+  private final OpenMetrics2Properties openMetrics2Properties;
 
   /**
    * Map that stores metric-specific properties keyed by metric name in exposition format
@@ -111,7 +113,8 @@ public static Builder builder() {
       ExporterFilterProperties exporterFilterProperties,
       ExporterHttpServerProperties httpServerConfig,
       ExporterPushgatewayProperties pushgatewayProperties,
-      ExporterOpenTelemetryProperties otelConfig) {
+      ExporterOpenTelemetryProperties otelConfig,
+      OpenMetrics2Properties openMetrics2Properties) {
     this.defaultMetricsProperties = defaultMetricsProperties;
     this.metricProperties = metricProperties;
     this.exemplarProperties = exemplarProperties;
@@ -120,6 +123,7 @@ public static Builder builder() {
     this.exporterHttpServerProperties = httpServerConfig;
     this.exporterPushgatewayProperties = pushgatewayProperties;
     this.exporterOpenTelemetryProperties = otelConfig;
+    this.openMetrics2Properties = openMetrics2Properties;
   }
 
   /**
@@ -167,6 +171,10 @@ public ExporterOpenTelemetryProperties getExporterOpenTelemetryProperties() {
     return exporterOpenTelemetryProperties;
   }
 
+  public OpenMetrics2Properties getOpenMetrics2Properties() {
+    return openMetrics2Properties;
+  }
+
   public static class Builder {
     private MetricsProperties defaultMetricsProperties = MetricsProperties.builder().build();
     private final MetricPropertiesMap metricProperties = new MetricPropertiesMap();
@@ -180,6 +188,8 @@ public static class Builder {
         ExporterPushgatewayProperties.builder().build();
     private ExporterOpenTelemetryProperties otelConfig =
         ExporterOpenTelemetryProperties.builder().build();
+    private OpenMetrics2Properties openMetrics2Properties =
+        OpenMetrics2Properties.builder().build();
 
     private Builder() {}
 
@@ -231,6 +241,18 @@ public Builder exporterOpenTelemetryProperties(
       return this;
     }
 
+    public Builder enableOpenMetrics2(Consumer<OpenMetrics2Properties.Builder> configurator) {
+      OpenMetrics2Properties.Builder openMetrics2Builder = OpenMetrics2Properties.builder();
+      configurator.accept(openMetrics2Builder);
+      this.openMetrics2Properties = openMetrics2Builder.build();
+      return this;
+    }
+
+    public Builder openMetrics2Properties(OpenMetrics2Properties openMetrics2Properties) {
+      this.openMetrics2Properties = openMetrics2Properties;
+      return this;
+    }
+
     public PrometheusProperties build() {
       return new PrometheusProperties(
           defaultMetricsProperties,
@@ -240,7 +262,8 @@ public PrometheusProperties build() {
           exporterFilterProperties,
           exporterHttpServerProperties,
           pushgatewayProperties,
-          otelConfig);
+          otelConfig,
+          openMetrics2Properties);
     }
   }
 }

prometheus-metrics-config/src/main/java/io/prometheus/metrics/config/PrometheusPropertiesLoader.java

@@ -40,6 +40,7 @@ public static PrometheusProperties load(Map<Object, Object> externalProperties)
         ExporterPushgatewayProperties.load(propertySource);
     ExporterOpenTelemetryProperties exporterOpenTelemetryProperties =
         ExporterOpenTelemetryProperties.load(propertySource);
+    OpenMetrics2Properties openMetrics2Properties = OpenMetrics2Properties.load(propertySource);
     validateAllPropertiesProcessed(propertySource);
     return new PrometheusProperties(
         defaultMetricsProperties,
@@ -49,7 +50,8 @@ public static PrometheusProperties load(Map<Object, Object> externalProperties)
         exporterFilterProperties,
         exporterHttpServerProperties,
         exporterPushgatewayProperties,
-        exporterOpenTelemetryProperties);
+        exporterOpenTelemetryProperties,
+        openMetrics2Properties);
   }
 
   // This will remove entries from propertySource when they are processed.

prometheus-metrics-config/src/test/java/io/prometheus/metrics/config/OpenMetrics2PropertiesTest.java

@@ -0,0 +1,137 @@
+package io.prometheus.metrics.config;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
+
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class OpenMetrics2PropertiesTest {
+
+  @Test
+  void load() {
+    OpenMetrics2Properties properties =
+        load(
+            new HashMap<>(
+                Map.of(
+                    "io.prometheus.open_metrics2.content_negotiation",
+                    "true",
+                    "io.prometheus.open_metrics2.disable_suffix_appending",
+                    "true",
+                    "io.prometheus.open_metrics2.composite_values",
+                    "true",
+                    "io.prometheus.open_metrics2.exemplar_compliance",
+                    "true",
+                    "io.prometheus.open_metrics2.native_histograms",
+                    "true")));
+    assertThat(properties.getContentNegotiation()).isTrue();
+    assertThat(properties.getDisableSuffixAppending()).isTrue();
+    assertThat(properties.getCompositeValues()).isTrue();
+    assertThat(properties.getExemplarCompliance()).isTrue();
+    assertThat(properties.getNativeHistograms()).isTrue();
+  }
+
+  @Test
+  void loadInvalidValue() {
+    assertThatExceptionOfType(PrometheusPropertiesException.class)
+        .isThrownBy(
+            () ->
+                load(
+                    new HashMap<>(
+                        Map.of("io.prometheus.open_metrics2.content_negotiation", "invalid"))))
+        .withMessage(
+            "io.prometheus.open_metrics2.content_negotiation: Expecting 'true' or 'false'. Found:"
+                + " invalid");
+    assertThatExceptionOfType(PrometheusPropertiesException.class)
+        .isThrownBy(
+            () ->
+                load(
+                    new HashMap<>(
+                        Map.of("io.prometheus.open_metrics2.disable_suffix_appending", "invalid"))))
+        .withMessage(
+            "io.prometheus.open_metrics2.disable_suffix_appending: Expecting 'true' or 'false'."
+                + " Found: invalid");
+    assertThatExceptionOfType(PrometheusPropertiesException.class)
+        .isThrownBy(
+            () ->
+                load(
+                    new HashMap<>(
+                        Map.of("io.prometheus.open_metrics2.composite_values", "invalid"))))
+        .withMessage(
+            "io.prometheus.open_metrics2.composite_values: Expecting 'true' or 'false'. Found:"
+                + " invalid");
+    assertThatExceptionOfType(PrometheusPropertiesException.class)
+        .isThrownBy(
+            () ->
+                load(
+                    new HashMap<>(
+                        Map.of("io.prometheus.open_metrics2.exemplar_compliance", "invalid"))))
+        .withMessage(
+            "io.prometheus.open_metrics2.exemplar_compliance: Expecting 'true' or 'false'. Found:"
+                + " invalid");
+    assertThatExceptionOfType(PrometheusPropertiesException.class)
+        .isThrownBy(
+            () ->
+                load(
+                    new HashMap<>(
+                        Map.of("io.prometheus.open_metrics2.native_histograms", "invalid"))))
+        .withMessage(
+            "io.prometheus.open_metrics2.native_histograms: Expecting 'true' or 'false'. Found:"
+                + " invalid");
+  }
+
+  private static OpenMetrics2Properties load(Map<String, String> map) {
+    Map<Object, Object> regularProperties = new HashMap<>(map);
+    PropertySource propertySource = new PropertySource(regularProperties);
+    return OpenMetrics2Properties.load(propertySource);
+  }
+
+  @Test
+  void builder() {
+    OpenMetrics2Properties properties =
+        OpenMetrics2Properties.builder()
+            .contentNegotiation(true)
+            .disableSuffixAppending(true)
+            .compositeValues(false)
+            .exemplarCompliance(true)
+            .nativeHistograms(false)
+            .build();
+    assertThat(properties.getContentNegotiation()).isTrue();
+    assertThat(properties.getDisableSuffixAppending()).isTrue();
+    assertThat(properties.getCompositeValues()).isFalse();
+    assertThat(properties.getExemplarCompliance()).isTrue();
+    assertThat(properties.getNativeHistograms()).isFalse();
+  }
+
+  @Test
+  void builderEnableAll() {
+    OpenMetrics2Properties properties = OpenMetrics2Properties.builder().enableAll().build();
+    assertThat(properties.getContentNegotiation()).isTrue();
+    assertThat(properties.getDisableSuffixAppending()).isTrue();
+    assertThat(properties.getCompositeValues()).isTrue();
+    assertThat(properties.getExemplarCompliance()).isTrue();
+    assertThat(properties.getNativeHistograms()).isTrue();
+  }
+
+  @Test
+  void defaultValues() {
+    OpenMetrics2Properties properties = OpenMetrics2Properties.builder().build();
+    assertThat(properties.getContentNegotiation()).isFalse();
+    assertThat(properties.getDisableSuffixAppending()).isFalse();
+    assertThat(properties.getCompositeValues()).isFalse();
+    assertThat(properties.getExemplarCompliance()).isFalse();
+    assertThat(properties.getNativeHistograms()).isFalse();
+  }
+
+  @Test
+  void partialConfiguration() {
+    OpenMetrics2Properties properties =
+        OpenMetrics2Properties.builder().contentNegotiation(true).compositeValues(true).build();
+    assertThat(properties.getContentNegotiation()).isTrue();
+    assertThat(properties.getDisableSuffixAppending()).isFalse();
+    assertThat(properties.getCompositeValues()).isTrue();
+    assertThat(properties.getExemplarCompliance()).isFalse();
+    assertThat(properties.getNativeHistograms()).isFalse();
+  }
+}